The present invention relates to a vaulted tank and, more particularly, to an above-ground storage tank for flammable liquids.
Since the 1970s, the world and the United States have been concerned with the environment and the contamination of that environment, including the earth's soil, its atmosphere and its water. The first Earth Day in 1970 resulted in the eventual creation of the Environmental Protection Agency by the United States Congress.
One of the many problems which the Environmental Protection Agency has addressed is the deterioration of large, underground storage tanks which result in the leakage of contaminants into the soil, such as the deterioration of gasoline station storage tanks and the leakage of gasoline and diesel fuel into the surrounding water table.
To correct this problem, the EPA has suggested that all fuel storage tanks be placed above ground. This has created a classic confrontation between governmental departments. For example, the fire departments of most major cities prefer that fuel storage tanks be placed below ground to reduce fire hazard. Most municipal codes have been drafted with this concern in mind. In more recent years, the creation of large concrete entombed, above ground tanks has been suggested as a solution to the problem. That is, a gasoline storage tank may be entombed in concrete and placed above the ground to enable its surfaces to be easily checked for deterioration and fluid leakage. By entombing the fuel tank in concrete, the tank is made impervious to impact from a vehicle that might back into it, for example, and resistant to fire due to the insulating effect of the concrete The concrete insulation also provides the minimum two-hour fire resistive protection required by the Uniform Fire Code for above ground tanks. One example of such an entombed tank is shown in U.S. Pat. No. 4,826,644, issued May 2, 1989 to T. R. Lindquist and R. Bambacigno.
The concrete entombed tank has several disadvantages including cost and convenience. For example, a 1,000-gallon concrete entombed tank weighs 18,000 pounds after it has been manufactured. Such a tank requires a large truck and crane with at least two 20-ton nylon straps to transport the tank to the site where it is to be used and to then place the tank in the desired position. The concrete entombed tank is provided with bottom supporting feet to permit the inspection of its bottom surface during its use. In California, where earthquakes represent a real concern, concrete shoes are placed on the site on either side of the bottom supporting feet to prevent the movement of the tank during an earthquake. The placement of the concrete tank between the concrete shoes can be a very dangerous procedure in view of the tank's weight.